Main outcome measures: The primary end point was complete healing of the largest eligible ulcer. The primary outcome was time to complete healing of the reference ulcer. Secondary outcomes were: time to debridement, cost of treatments, health-related quality of life (including ulcer-related pain), bacterial load, presence of methicillin-resistant Staphylococcus oureus and staff and patient attitudes to and beliefs about larval therapy.

Results: Between July 2004 and May 2007 the trial recruited 267 people aged 20-94 years at trial entry. There were more female (n = 158) than male (n = 109) participants and most ulcers were classified by the nurse as having an area greater than 5 cm(2). The time to healing for the three treatment arms was compared using the log rank test. The difference in time to healing in the three treatments was not statistically significant at the 5% level. Adjustment was then made for stratification and prespecified prognostic factors (centre, baseline ulcer area, ulcer duration and type of ulcer) using a Cox proportional hazards model. No difference was found in healing rates between the loose and bagged larvae groups. Results for larvae (loose and bagged pooled) compared with hydrogel showed no evidence of a difference in time to healing. When the same analytical steps were used to investigate time to debridement, larvae-treated ulcers debrided significantly more rapidly than hydrogel-treated ulcers; however, the difference in time to debridement between loose and bagged larvae was not significant. The adjusted analysis reported the hazard of debriding at any time for those in loose and bagged larvae groups as approximately twice that of the hydrogel group. No differences in health-related quality of life or bacteriology were observed between trial arms. Larval therapy was associated with significantly more ulcer-related pain than hydrogel. Our base-case economic evaluation showed large decision uncertainty associated with the cost-effectiveness of larval therapy compared with hydrogel, suggesting that larval therapy and hydrogel therapy have similar costs and effects in the treatment of sloughy and/or necrotic leg ulcers.

Conclusions: Larval therapy significantly reduced the time to debridement of sloughy and/or necrotic, chronic venous and mixed venous/arterial leg ulcers, compared with hydrogel; however, larval therapy did not significantly increase the rate of healing of the ulcers. It was impossible to distinguish between larval therapy and hydrogel in terms of cost-effectiveness. Future research should investigate the association of debridement and healing and the value of debridement as a clinical outcome for patients and clinicians. To inform decision-makers' selection of debriding agents where debridement is the treatment goal, decision analytic modelling of all alternative debridement treatments is required.